1. Field of the Invention
The present invention relates to an inspection apparatus for foreign matter and pattern defects which is used in the process of manufacturing semiconductor devices.
2. Description of the Background Art
FIG. 12 is a perspective view of a prior art inspection apparatus for foreign matter and pattern defects which is disclosed in Japanese Patent Application Laid-Open No. P11-51622A (1999).
A foreign matter inspection apparatus 10P comprises an inspection illumination device 20P for directing inspection light (laser light) 21P angularly toward a wafer 1P, and a scattered light detector 34P for detecting resultant scattered light 31P from the wafer 1P under dark field illumination, thereby determining the coordinate position of foreign matter 5P. The foreign matter inspection apparatus 10P further comprises a reflection type illumination device 40P and an image pickup device 45P. The image pickup device 45P photographs the coordinate position of the foreign matter 5P determined by a foreign matter judgement device 35P based on the detection of the scattered light detector 34P under bright field illumination provided by the reflection type illumination device 40P. The foreign matter inspection apparatus 10P extracts a foreign matter image, based on the photograph, and then specifies the size, shape, color, and property of the foreign matter, based on the extracted foreign matter image.
In FIG. 12, the reference character 2P designates a first main surface; 3P designates an orientation flat; 4P designates a pellet; 11P designates a stage device; 12P designates an XY table; 13P designates a .theta. table; 14P designates a controller; 22P designates a laser light irradiating device; 23P designates a condensing lens; 30P designates a scattered light detecting device; 32P designates an objective lens; 33P designates a relay lens; 41P designates white light; 42P designates a white light irradiating device; 43P designates a half mirror; 44P designates a lens; 46P designates an image processor; 47P designates a comparator; 48P designates a verifier; and 49P designates a classifier.
Foreign matter and defects are of a variety of types. For example, some foreign matter affects yields, and some foreign matter does not affect yields. Some objects look like foreign matter or defects, but actually are, for example, grain patterns such as an elongated grain boundary of an aluminum film and scratches resulting from a chemical-mechanical polishing (CMP) process.
However, the use of the image pickup device 45P for inspection for foreign matter and defects sometimes requires very long time. First, the image pickup device 45P performs focusing and magnifying actions to photograph the surface of the wafer 1P, thereby detecting surface information (a microscope image) from the wafer 1P. Next, the foreign matter inspection apparatus 10P extracts image information regarding foreign matter and defects from the microscope image photographed by the image pickup device 45P to identify foreign matter and defects. If numerous, e.g. thousands of to tens of thousands of, pieces of foreign matter and defects are detected, the above described operations require quite long time and impractical, and it is very difficult to grasp an overview of all of the foreign matter and defects within a predetermined length of time. Additionally, the microscope image is an image of the wafer 1P as viewed from above and shows only the plan configuration of the foreign matter and defects. This makes it difficult to judge whether or not the identified foreign matter and defects affect the yields.
Another method of identifying the foreign matter and defects on the wafer surface uses laser light. Laser light directed onto the wafer and scattered therefrom is detected for detection of surface information from the wafer. This method does not require the focusing and magnifying actions to detect the surface information from the wafer accordingly more quickly than the technique employing the image pickup device 45P. This shortens the time required for inspection for the foreign matter and defects. However, this method is disadvantageous in that the light scattered from a pattern defect, a fine foreign particle and a scratch-type defect is low in intensity, resulting in decreased sensitivity of detection of these defects or, in some cases, failure to detect these defects.
As described above, the method employing the microscope and the method employing the laser light have both advantages and disadvantages and present great difficulties in effectively distinguishing the above-mentioned types of foreign matter and defects from each other, based on the wafer surface information.